1. Field of the Invention
The present invention relates to a lens unit and to devices employing the lens unit to form or scan images.
2. Description of the Related Art
Optical systems having linear arrays of optical elements that form erect images with one-to-one magnification are used in various image forming and image scanning devices incorporating arrays of light-emitting or light-sensing elements. Exemplary devices include electrophotographic printers with arrays of light-emitting diodes (LEDs) and image scanners with optical line sensors. Japanese Patent Application Publication No. 2008-83576 proposes an array of paired microlenses for use in this type of optical system.
In both image forming devices and image scanning devices, there is a need for optical systems with improved optical efficiency. In the optical exposure devices or ‘heads’ of electrophotographic printers, for example, to increase the resolution of the printed image, the light-emitting elements must be packed densely together. Their size is consequently reduced, with a corresponding reduction in emitted light. The optical efficiency of the optical system must be increased in compensation so that a bright image can be formed despite the reduced amount of light. In scanning devices, the optical efficiency of the optical system needs to be improved to reduce power consumption by the light source that illuminates the document or other subject copy being scanned.